private void button1_Click(object sender, EventArgs e)
 {
     if (string.IsNullOrEmpty(txtFullname.Text) || Convert.ToInt32(lblID.Text) <= 0)
     {
         MessageBox.Show("One or more field haven't been filled correctly");
         return;
     }
     if (libraryApp.UpdateAccount(Convert.ToInt32(lblID.Text), txtFullname.Text.Trim(), txtAddress.Text.Trim(), txtPhone.Text.Trim()))
     {
         MessageBox.Show("Update Success");
     }
     else
     {
         MessageBox.Show("Error occurred\n Please relogin if the error continues!");
     }
 }